The present invention relates generally to methods and devices for mechanically assisting the failing heart. More specifically, it relates to balloon catheters and bypass pumps.
Many types of cardiac assist devices have been developed over the past 40 years. The general types of devices can be characterized as short-term (hours to days), bridge-to-transplantation, bridge-to-recovery, and permanent or long-term. The goal of these devices is to mechanically support the failing heart by increasing systemic perfusion, and/or reducing the workload of the failing heart, thus creating the most favorable environment for cardiac recovery.
Short-term devices are used on patients whose hearts have sustained a serious injury but can recover if adequately supported. The most commonly used short-term device is the intra-aortic balloon pump (xe2x80x9cIABPxe2x80x9d). Indications for employment of the IABP include cardiogenic shock or severe heart failure secondary to acute myocardial infarction or following open-heart surgery, unstable angina resistant to drug therapy, and refractory ventricular irritability after myocardial infarction. The following patents disclose intra-aortic balloon pumps. The full disclosures of these patents are all incorporated herein by this reference:
The following patents disclose intra-aortic balloons. The full disclosures of these patents are all incorporated herein by this reference:
Aortic occlusion balloons are known in the prior art. Such aortic balloons are non co-pulsating with the heartbeat and are not employed with an aortic bypass pump. The following patents disclose aortic occlusion balloons. The full disclosures of these patents are all incorporated herein by this reference:
The basic components of the intra-aortic balloon pump (xe2x80x9cIABPxe2x80x9d) are a catheter tipped with a long balloon and a pump console that shuttles helium gas through the catheter to inflate and deflate the balloon synchronously with the heart beat. The balloon is inserted into an artery and guided to a position in the descending thoracic aorta just distal to the left subclavian artery. The pump control console contains signal processing, drive, timing, and control mechanisms for appropriate inflation and deflation. During cardiac systole ventricular contraction and ejection, the IABP is rapidly deflated, reducing the workload and oxygen demands of the heart by decreasing the resistance to blood flow from the ventricle. During cardiac diastole ventricular relaxation and filling, the IABP is rapidly inflated counter-pulsation increasing aortic and coronary perfusion pressures. Timing of the inflation-deflation cycle is based on the electrocardiogram and arterial blood pressure waveform.
When heart failure is severe, the IABP cannot provide adequate circulatory support because it cannot replace cardiac function. The treatment of severe heart failure requires the use of cardiac-bypass blood pumps. These devices are more invasive than the IABP and employ direct cannulation of the ventricle or atrium. Implantation and removal of the cardiac cannulas may further injure the heart and be associated with bleeding complications. It is estimated that nearly 100,000 patients worldwide underwent short-term mechanical circulatory support during 2000. The following patents disclose cardiac bypass pumps. The full
Aortic bypass pumps are known in the prior art. Aortic bypass pumps are not employed with a co-pulsating aortic occlusion balloon for heart assistance. The following patents disclose aortic bypass pumps. The full disclosures of these patents are all incorporated herein by this reference:
Because of the limitations of aortic bypass pumps, intra-aortic balloon pumps, and the complications associated with cardiac bypass pumps, there is a need for an improved short-term heart-assist device.
A preferred embodiment of the present invention provides a method and a system to temporarily assist the failing heart. The temporary heart-assist system comprises an occluding device positionable in the patient""s descending aorta. The occluding device may or may not include a pressure sensor that electrically couples to an extra-corporeal controller. The occluding device itself also couples pneumatically to the extra-corporeal controller. The pump inlet of an extra-corporeal pump is connectable via a cannula to a patient""s supra-diaphragmatic artery. The pump outlet of the extra-corporeal pump is connectable via a cannula to a patient""s infra-diaphragmatic artery.
In the method of the present invention, a doctor inserts into the patient the occluding device via a peripheral artery into the descending aorta, and positions the occluding device near the level of the patient""s diaphragm. The occluding device catheter, coupled to the extra-corporeal controller, inflates and deflates the occluding device. The electrocardiogram ECG and proximal aortic blood pressure, measured in the upper arterial compartment via a lumen in the occluding device catheter, serve as inputs to cycle the occluding device synchronously with the heartbeat. The step of inflating occurs just prior to the start of cardiac systole co-pulsation and ventricular ejection. The extra-corporeal pump continuously or cyclically pumps blood from a supra-diaphragmatic artery to a infra-diaphragmatic artery. The pumping flow rate varies in response to the end-systolic pressure measured in the upper arterial compartment of the patient""s body. The step of deflating the aortic balloon occurs at the start of cardiac diastole and aortic valve closure. Deflating the balloon stabilizes the perfusion pressure between the upper and lower arterial compartments.
In another feature of the present invention, the method of the present invention pumps blood from the patient""s upper to the patient""s lower arterial compartments.
The present invention is designed to temporarily assist the failing human heart for a period of several hours to several days. The objectives of the heart-assist system of the present invention are to augment cardiac output and enhance systemic perfusion, reduce the workload and oxygen requirements of the acutely failing heart and allow for its recovery, allow for optimization of concomitant drug therapy, require minimal surgical intervention for insertion and removal, and reduce additional trauma to the failing heart by eliminating a need for direct cannulation of the left atrium or left ventricle. An additional feature of this technology is enhancement of diastolic perfusion by elevation of pressure throughout the diastolic interval and, unlike a commercially available balloon pump, enhancement of perfusion to all organs.
The present invention allows for treatment of the failing heart in a minimally invasive manner with augmentation of left ventricular stoke volume cardiac output and simultaneous reduction in left ventricular workload and oxygen requirements of the heart.
An important feature of the invention is that it rapidly inflates a small-volume balloon, partially occluding the aorta just prior to the start of cardiac systole and ventricular ejection. In another feature of the invention, it regulates aorta-aorta bypass blood pump flow to obtain a specific end-systolic aortic pressure measured in the upper arterial compartment. In another feature of the invention, decreasing end-systolic aortic pressure results in an increased ventricular stroke volume based on the ventricular pressure-volume-contractility relationship. Decreased systolic pressure also reduces the workload on the failing heart. Increased bypass pump blood flow elevates perfusion pressure in the lower arterial compartment. In another feature of the invention, during ventricular diastole, the system rapidly deflates an aortic balloon at end-systole. Deflating the aortic balloon stabilizes the perfusion pressure between the upper and lower arterial compartments.